Emergency calling services are widely utilized and relied upon. In the United States, the “911” emergency calling system handles approximately 500,000 calls daily. Emergency calls in the existing emergency services network in North America are routed to an emergency response center known as a Public Safety Answering Point (“PSAP”). In particular, the call is routed to the PSAP that serves the caller's current location. The calling party number is obtained from Automatic Number Identification (“ANI”) equipment. ANI is a system utilized by telephone companies to identify the Directory Number (“DN”) of a calling subscriber. A pre-configured database known as an Automatic Location Identification (“ALI”) database is used to identify the caller's location. The ALI database typically contains location information for subscribers in the public telephone network, maintained by the service provider, and is supplemented with a second database, the PS ALI database, which contains location information for telephone numbers assigned to private (enterprise) networks with location information provided and maintained by the private enterprises. The results from the ANI and ALI searches is provided to the PSAP so that the call taker is provided with a callback number and location. The callback number enables the call taker to attempt to re-establish contact with the emergency caller in the event of disconnect. The location information may be used to direct responders, particularly in the situation where the caller is unable to provide their location to the call taker.
Within an enterprise network, the selection of the ANI to be sent to the PSAP to identify the caller's location is typically based on Emergency Response Locations (“ERLs”). ERLs are zones within the enterprise such as floor, post, section and other designator with which pre-assigned numbers are associated. Each pre-assigned number (“ELIN”) has, when defined, an entry made in the ALI database to describe the ERL it represents within the enterprise. With Voice over Internet Protocol (“VoIP”) systems, the location of the caller must be dynamically associated with an ERL based on the current location of the IP phone that the caller is using. In an emergency services network such as that described by the National Emergency Number Association (“NENA”) in their I3 specification and currently being defined within the IETF and other standards bodies, the legacy procedure of using ANI to convey location to the PSAP and the use of specific PSTN access points to reach the correct PSAP will become obsolete. Location information, probably in the form of IETF GEOPRIV PIDF-LO location records containing Civil and/or coordinate location of the caller will be passed to the PSAP with the emergency call. However, in the interim, where VoIP callers exist prior to the widespread implementation of the evolved “I3 PSAP,” or equivalent services by carriers to accept VoIP emergency calls with location information explicitly attached, there is a need to continue to use existing mechanisms to access the emergency services network for VoIP callers. This is problematic because an emergency call that is formatted to reach an “I3” PSAP is not directly compatible with the existing emergency network. Similarly, as I3 PSAPs start to be deployed there will be situations where an I3 PSAP is available in some areas and not in others, particularly when service across multiple countries is considered. The invention also enables the adaptation of signaling from a PBX, that is designed to interface to the existing emergency services network, to interface to an I3 PSAP in areas where they are deployed.